A variety of hand actuated mechanical devices have been devised over the years to lock the shifter arm of an engine transmission shift control at one or more desired positions. Examples of such devices are disclosed in U.S. Pat. No. 2,895,347 which discloses a hand operated friction device and in U.S. Pat. Nos. 2,703,499 and 3,727,482 which respectively disclose spring loaded tilting mechanisms and in U.S. Pat. No. 1,629,666 which discloses a hand-releasable pin for locking the shifter control at prescribed indentations in a locking arm, the disclosures all of which are included herein by reference.
The problem with the above devices and other such hand actuated devices is that they rely upon an act by the operator for their respective operation and are not completely independent of the operator which in many instances may be particularly desirable. One such instance is the need to protect the gear train of an engine transmission from shock and wear and possible damage from shifting from and through neutral to engage a particular gear while the engine speed is relatively high. Such shifting arises, for example, when refuse haulers make frequent stops at short distances and attempt to shift from and through neutral while the vehicle engine is running at relatively high speed.
In view of the above, a need exists to automatically prevent an operator from shifting an automatic transmisson from and through netural to engage a gear above a predetermined engine speed value to prevent undue wear and/or damage to the transmission yet enables shifting from and through netural to engage a gear of the transmission when the engine speed falls below the predetermined engine speed value.